(1) Field of the Invention
The present invention relates to a projection type LCD projector, and in particular is directed to angle control of the illumination light of the liquid crystal display in an LCD projector.
(2) Description of the Prior Art
In conventional projection type LCD systems such as LCD projectors, light rays emitted from the light source lamp are radiated to liquid crystal light valves, where the radiated light rays are modulated in accordance with the image to be displayed so as to form a projected image on the screen by way of the projection optical system.
However, a further improvement in luminance has been demanded in order to achieve improvement of high-efficiency design for the optical system, for using a high-power light source lamp, or for a system using a multiple number of illumination lamps. For example, the usefulness of a system including a multiple number of illumination lamps is evaluated based on the lighting control function of controlling the number of the lamps or the countermeasure against the loss or damage of one of the lamps.
As disclosed in Japanese Patent Application Laid-Open Hei 11 No.96803 and xe2x80x98Gekkan Display(Monthly Display)xe2x80x99 Vol.5 No.4 issued by Techno-Times, April 1999, a light source device for a projection type display using a plurality of illuminating light sources has been disclosed.
Now, this light source device will be described with reference to the drawings. FIG. 1 is a schematic view showing the configuration of optical elements in a conventional projection type display.
As shown in FIG. 1, the configuration of the light source device includes: for example, light sources 1 and 2; reflectors 3 and 4 for reflecting light rays emitted from light sources 1 and 2; and a reflection mirror 29 for reflecting the light rays, which are reflected by reflectors 3 and 4, in the same direction. The reflectors 3 and 4 are arranged opposing each other with reflection mirror 29 in between. This reflection mirror 29 has two facets being arranged in an inverted V geometry, being inclined 45xc2x0 with respective reflectors 3 and 4.
Light rays emitted from light source 1 and reflected by reflector 3 and light rays emitted from light source 2 and reflected by reflector 4 are reflected by reflection mirror 29 in the same direction and pass through a pair of fly-eye lenses 6 and 7 and polarizer 8, being focused by condenser lenses 9 to 14 and color separation/reflection mirrors 15 to 20, onto video signal conversion light valves 21 to 23. Video signals for three color separation components are integrated into one optical path by means of a color composition prism 24 so that the composited image is enlarged and projected by a projection lens 25.
However, in the above configuration, since the angular characteristics of the incident light on color separation/reflection mirrors 15 to 20, color composition prism 24 and projection lens 25 differ between the light from light source 1 and that from light source 2, there occurs the color unevenness problem due to the difference in luminance between light sources 1 and 2 or the color unevenness problem arising during projection with one light source.
Now, comparison as to angular distributions of incident rays will described with reference to the drawings.
FIG. 2 is a graph showing the angular distributions of the intensity of light incident on a mirror using the conventional reflection mirror. FIG. 3A is an illustrative view showing the optical paths when the conventional reflection mirror is used. FIG. 3B is an illustrative view showing the distribution of the intensity of light with the conventional reflection mirror.
Angular distributions of the intensity of light incident on a mirror using the conventional reflection mirror, as shown in FIG. 2, represent the intensity of light depending on the incidence angle of light rays from light sources 1 and 2 incident on a color separation/reflection mirror 15. It is understood from FIG. 1 that the color separation spectral characteristics of color separation/reflection mirror 15 differ depending on the difference in angular distribution between incident light from light source 1 and that from light source 2. This is why color unevenness occurs.
Next, concerning the distribution of the intensity of light rays from light source 1 at the pupil of the projection lens, FIGS. 3A and 3B represent the distribution of the intensity of light at the center (the LCD center) of the image height on the object plane of the projection lens. Since the picked up intensity of light varies as the image height changes, the pupil will become compressed as the image height is greater. Therefore, the pickup light intensity at the projection lens deviates and hence disturbs the color balance due to the difference in design of the angular distribution of the B-ch light rays which are once inverted, from the angular distributions of the R-ch and G-ch light rays. Thus, color unevenness occurs in the resultant enlarged projected image.
The present invention has been devised in view of the above conventional problems and it is therefore an object of the present invention to provide a projection type display which is improved to reduce color unevenness, without causing any offset of the angular distributions of light rays through the color separation mirrors, color composition prism and projection lens, attributed to the light sources.
In order to achieve the above object, the present invention is configured as follows:
In accordance with the first aspect of the present invention, a projection type display, wherein light rays emitted from light sources pass through an integrator including fly-eye lenses and proceed through predetermined light paths including condenser lenses and are focused on liquid crystal light valves of liquid crystal panels or the like, where the light rays are converted into video information, includes: a plurality of light sources; a plurality of reflectors for condensing the light rays from the light sources; and a multiple number of separation/reflection means for dividing the light rays condensed by the reflectors in the substantially same direction into multiple elongate rectangular sections.
In accordance with the second aspect of the present invention, the projection type display having the above first feature is characterized in that the width of the reflection light rays divided by the separation/reflection means is set equal to an integral multiple of a single cell width of the fly-eye lens.
In accordance with the third aspect of the present invention, the projection type display having the above first feature is characterized in that the separation/reflection means is made up of a multiple number of prisms being arranged in an array, each having the two sides defining the right-angled portion formed with a reflective coating.
In accordance with the fourth aspect of the present invention, the projection type display having the above second feature is characterized in that the separation/reflection means is made up of a multiple number of prisms being arranged in an array, each having the two sides defining the right-angled portion formed with a reflective coating.
In accordance with the fifth aspect of the present invention, the projection type display having the above first feature is characterized in that the separation/reflection means is made up of a multiple number of glass substrates having reflective portions and transparent portions formed alternately thereon, the glass substrates being arranged in a zigzag manner.
In accordance with the sixth aspect of the present invention, the projection type display having the above second feature is characterized in that the separation/reflection means is made up of a multiple number of glass substrates having reflective portions and transparent portions formed alternately thereon, the glass substrates being arranged in a zigzag manner.
In accordance with the seventh aspect of the present invention, the projection type display having the above first feature is characterized in that the separation/reflection means is configured of prisms arranged in an array, the opposing side of the right-angled portion of each prism being used as the reflective surface.
In accordance with the eighth aspect of the present invention, the projection type display having the above second feature is characterized in that the separation/reflection means is configured of prisms arranged in an array, the opposing side of the right-angled portion of each prism being used as the reflective surface.
In accordance with the ninth aspect of the present invention, the projection type display having one of the above first through eighth features further comprises a control means for activating and deactivating the multiple number of light sources.
According to the present invention, provision of multiple light sources and multiple reflectors for condensing the light rays from the light sources makes it possible to enhance the luminance of projection light. Further, provision of a separation/reflection means for dividing the light rays condensed by the reflectors in the substantially same direction into multiple elongate rectangular sections makes it possible to provide offset-free angular distributions of light rays incident on the color separation/reflection mirror and offset-free angular distributions of light rays incident on the projection lens, whereby it is possible to reduce color unevenness of the projected image.
Since the width of the reflection light rays divided by the separation/reflection means is set equal to an integral multiple of a single cell width of the fly-eye lens, it is possible to produce offset-free angular distributions of light rays incident on the color separation/reflection mirror and incident on the projection lens.
Since the separation/reflection means is made up of a multiple number of prisms being arranged in an array, each having the two sides defining the right-angled portion formed with a reflective coating, the necessary functions can be achieved by a simple configuration using a multiple number of small reflective mirrors in a minimum space.
Since the separation/reflection means uses glass substrates having reflective mirror coatings, the same effect as above can be obtained by a low-price configuration.
Since the opposing side of the right-angled portion of each prism is made use of based on the total reflection principle as the reflective surface in the separation/reflection means, it is possible to reduce color unevenness across the projected image in a more improved manner than when reflective coatings are used.
Since provision of a control means for activating and deactivating the multiple number of light sources makes it possible to provide a lighting system using ON/OFF combination of the multiple light sources, thus providing a further improved distribution of the intensity of light.